Direct link of a feature type with a table or a query of EDB is set by specifying the field of this table (query) which should contain internal number of feature linked with the corresponding record of the table or query. For brevity such a field will be called field of direct link below. Filling of the field of direct link will be performed automatically when the link of a record with a feature is set.
It is supposed that the user who performs linking of the feature with the record has a permission to set values of the field of direct link.
ObjectLand imposes a limitation on the type of field of direct link – the field should be integer, precision of field should be not less that 10 decimal digits.
To get records linked with map feature, ObjectLand forms a request to EDB. In SQL statement SELECT of the request the value of field of direct link is specified which corresponds to internal number of the feature. The set of records linked with map feature will be the result of the request. To increase the speed of getting records linked with the feature, it is advisable to create an index for the field of direct link in EDB table. Creation of an index is performed by external tools with respect to GIS ObjectLand.
To get the feature linked with the record, ObjectLand takes the value from the field of direct link of the record (that is, internal number of the feature linked with the record) and provides the user with a feature with specified internal number.
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